Elevator systems



Filed Jan. 2, 1959 4 Sheets-Sheet 1 Fig. l.

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Joins!!! 30 Y NJQ 5 ,5 ,5 awfm mo wmo A .W F '2 i 32 mo wwmo 3Q 32 32 -32 United States Patent ELEVATOR SYSTEMS George Macredis, Teaneck, NJ., assignor' to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 2, 1959, Serial No. 784,631

6 Claims. (Cl. 18729) This invention relates to elevator systems and it has particular relation to elevator systems wherein a plurality of elevator cars is arranged in a structure to operate as a bank.

It is well known that the demand for service from an elevator system in the average building varies appreciably throughout the day. For example, during the night in an office building the elevator system usually is required to provide very little service. This period is referred to an foil-hours period of operation. Similar infrequent demand for elevator service sometimes is encountered during the business day.

At the start of abusiness day a substantial demand for service in the up direction from the lower terminal floor occurs. This period is known as an up-peak period.

Immediately after the close of the business day, a peak demand for down service generally is encountered. Such a period is designated a down-peak" period.

During the remainder of the business day, the demand for elevator service in the two directions of travel may be substantially balanced. Such periods are known as fofi-peak periods.

Although aspects of the invention may be incorporated in elevator systems employing either a single elevator car or a number of elevator cars arranged in a bank, andalthough aspects of the invention may be incorporated in elevator systems arranged either for automatic opera- .tion or attendant operation, the invention may be considered adequately by reference to a bank of elevator cars arranged for automatic operation. For this reason, the following discussion will be directed primarily to such an elevator system.

In a bank of elevator cars arranged for automatic operation, theelevator cars may operate between two terminal floors which consist generally of an upper-terminal floor and a lower or street terminal floor. A plurality of intermediate floors is located between the two terminal floors.

Each of the elevator cars generally has a motor for moving the elevator car relative to the associated building structure. In a preferred embodiment of the invention, the motor is energized from the generator of an individual motor-generator set.

In order to provide for registration of calls for elevator service, suitable call-registering means are provided. Such call-registering means may include first call-registering means, including an operating member located at each of the floors from which elevator service is desired in a first direction, such as the up direction. In addition, the call-registering means may include second call-registering means including an operating member located at each of the floors from which elevator service is desired in a second direction, such as the down direction. Finally, third call-registering means may be provided for the purpose of registering calls for floors desired by the load within the elevator car. Such third call-registering means may include an operating member within the elevator car for each floor to which a passenger in the elevator car may desire to be transported.

To assist in controlling the spacing of the elevator cars, a dispatcher may be employed for controlling the departure of the elevator cars from each of the terminal floors. Although the dispatcher may be responsive to the number or location of registered calls for elevator service, in a preferred embodiment of the invention the dispatcher includes means for dispatching successive elevator cars from each of the terminal fioors at suitable dispatching intervals. The dispatcher may be of the rotational type but preferably a non-rotational dispatcher is employed.

To care for the traffic demand variations or the different traffic patterns encountered by the elevator system, different types or modes of operation are provided, each designed to cope with a specific traffic demand variation or pattern. The elevator system is transferred from one mode of operation to another mode of operation automatically.

The transfer between modes of operation maybe effected on a time basis. This may be suitable for an elevatorsystem serving a building occupied by a single company having employees who follow regular patterns during each business day. In such a case, a time clock may control the system to operate in a mode providing suitable up-peak, off-peak, down-peak and off-hours operation during definite time intervals of each day.

Preferably, the transfer between modes of operation is in response to the traffic demand itself. To illustrate this type of transfer, suitable operation of the system for various traffic patterns and suitable transfers between mode of operation will be outlined.

It will be assumed first that no demand for elevator service exists. Such absence of demand may occur during off-hours periods, such as nights, in office buildings. Under such circumstances, the elevator cars park at predetermined stations. Preferably, all elevator cars park at the lower-terminal floor. If a substantial time has elapsed since the last call for elevator service was answcred, the motor-generator sets of all of the cars may be stopped. One of the elevator cars parked at the lower terminal floors is selected as the next to leave the terminal floor.

When a call for elevator service is registered from one of the floors or if such a call is registered in the selected elevator car, the motor-generator set of the selected elevator car is started and the elevator car is dispatched to answer the registered call. The registered call also may be effective for energizing any other required equipment.

If an elevator car arrives at the parking floor with no call for elevator service registered by the system and with all other elevator cars parked with their motorgenerator sets shut down, the selection of the next elevator car to be dispatched is transferred to the arriving elevator car. Upon the expiration of a suitable interval without further calls for elevator service, the motor-generator set of the arriving car stops. The foregoing is illustrative of off-hours operation.

If calls for elevator service continue to be registered while the first selected elevator car is in operation, a successive elevator car starts and operates in the same manner discussed for the first selected elevator car upon the expiration of the dispatching interval of the dispatcher for the lower-terminal floor, and similarly for the remaining cars in the bank. Consequently for moderate demands for elevator service, the elevator cars may operate on through trips between terminal floors and may be dispatched at timed intervals from each of the terminal floors. Such operation, which'is substantially balanced in the 3. two directions of travel, is illustrative of elf-peak" operation.

In accordance with the invention, the interval between the dispatching of successive selected elevator cars from the'terrninal landings during off-peak operation is automatically varied. Such variation in dispatching interval is dependent upon the rate of all stops made by all of the elevator cars in the bank at all of the landings served by thee'levator bank when the bank is conditioned for offpeak operation. Thus if the rate of car stops exceeds a predetermined level, successive selected cars are (118- patched after the lapse of what may be termed a normal dispatching interval. However, if the rate of car stops is equal to or less than the predetermined level, the dispatching iri terval is increased. By virtue of such operation, efiicient elevator service is maintained during ofi-peak p'eriddsfbut wear and tear on the elevator equipment is minimized. It is to be understood that the dispatching intervals for the upper terminal floor need not be the same as those employed for the lower terminal floor.

The next operation of the elevator system to be considered will be that in which a substantial demand for elevator service in the up direction exists. To serve this traffic demand, the elevator system is transferred automatically'to a mode of operation which may be designated up-peak operation.

The demand for service in the up direction may be measured in various ways. In one embodiment of the invention, the service demand in the up direction is determined by a measurement of the rate of loading of elevator cars set for uptrav'el at the lower terminal floor. When this rate of loading exceeds a predetermined value, the system is automatically transferred to up-peak operation.

For up-peak operation, the elevator cars are placed in service successively as discussed for olT-hours operation, or the cars may be alreadyin off-peak operation at the time the up-peak occurs. For the up-peak, travel of the elevator cars in the up direction is expedited. I

When a substantial demand for elevator service in the down direction is registered, the elevator system may be transferred automatically to a mode of operation termed down-peak operation wherein service in the down direction is expedited in any suitable manner.

In elevator systems of the type thus far described, it has been the practice to allow the system to be returned automatically to off-peak or off-hours operation after the termination of up-peak or down-peakoperation. As heretofore noted, an up-peak period occurs at the start of a business day and a down-peak period occurs at the close 'of the business day. Thus, in prior art systems, the elevator system was returned to off-hours operation each time a substantial lull in traffic occurred during the day.

In accordance with a further aspect of the invention, the occurrence of an up-peak period prevents the return of the elevator system to off-hours operation until the subsequent occurrence of a down-peak period. 7 Thus, during'the business day the motor-generator sets of all of the elevator cars are maintained in running condition. As

a result thereof, upon the occurrence of heavy or peakperiods of trafiic, the elevator system is more promptly transferred to the required mode of operation, and the efficiency of operation of the system thereby is improved. As mentioned above, when a substantial lull in traflic does occur during the business day, the dispatching interval between successive selected elevator cars is increased.

it is, therefore, an object of the invention to provide an improved elevator system having a plurality of elevator cars and a dispatcher therefor wherein the dispatching interval between successive selected elevator cars is automatically varied in accordance with the rate of all stops made by all of the elevator cars.

'It is another object of the invention to provide an im- 7 proved elevator system as definedin the preceding object wherein'the elevatorsfystem has plural modesof operation the subsequent occurrence of a down-peak mode of op eration.

Other objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawings in which:-

Figure l is a schematic view with circuits shown in straight line form of a portion of an elevator control system embodying the invention.

Figs. 2, 3 and 4 are schematic views with circuits shown in straight line form of further portions of the elevator control system illustrated in Fig. 1; and

Figs. 1A, 2A, 3A and 4A are key representations of electromagnetic relays and switches employed in Figs, 1, 2, 3 and 4. If Figs. 1A, 2A, 3A and 4A are placed in horizontal alignment with Figs. 1, 2, 3 and 4, respectively,

it will be found that corresponding contacts, and coils' .of

relays and switches shown in the horizontally-aligned figures are substantially in horizontal alignment.

In order to simplify the presentationof the invention, it will be, described with reference to the systemshown in the Satini et' al. Patent 2,740,496 which issuedApril 3, 1956. Insofar as possible, the connections employed in theSantini et al. patent will be adhered to in the present discussion. Components of the Santini et al. patent which are herein illustrated will be identified by the .same refer ence characters employed in the Santini et al. patent.

As is noted in Fig. 1, the control system illustrated herein is intended to include all components of the con trol system of the Santini et al. patent and similar com-' ponents of the two systems operate'in identical manner. For this reason, a detailed discussion of the similar components of the two control systems is believed to be un necessary at the present time. It should be noted funther that the present'Fig. 1 includes a reproduction of the upper portion of Fig. 5 of the Santini et al. patent; the present Fig. 2'includes a reproduction of the lower portion of Fig. 8 of the Santini et al. patent; the present Fig. 3 includes a reproduction of the upper portion of Fig. 7 of the'Santini et al. patent; and the present Fig. 4'ineludes a reproduction of the upper portion of Fig. 8 of the' Santiniet al. patent.

Components which have been added to the Santini et al. system 'in order to illustrate the present invention are shown in Figs. 1, 2, 3 and 4 in heavy lines. For convenie'nce the following components appearing in the accompanying drawings are listed:

Figure I HCM High-call reversal relay QLl-Contacts of loaded-car quota relay QL 1 79Cam-operated switch 79C-Cam 7 9M-Induction motor Figure 2 Figure 3 K-Time-period relay N -aReset relay SSS teppingswitch- QB- Dispatching interval quota-relay SST-Upper dispatcher motor 89T--Cam 91T and 92T-Cam-operated switches DT-Upper dispatching interval relay 1SD-Upper-interval-holding relay DPlS-Contacts of down-peak relay DP Figure 4 85L-Lower dispatcher motor 89LCam 91L and 92LCam-operated switches DLLower dispatching interval relay DP16-Contacts of down-peak relay DP As is noted in the Santini et al. patent, the elevator system includes four elevator cars arranged for fully automatic operation. The four elevator cars are designated by the reference characters A, B, C and D. Components for the cars B, C and D which are similar to the components associated with the elevator car A are identified by the reference characters employed for the elevator car A preceded, respectively, by the prefixes B, C and D to indicate that the components are associated, respectively, with the elevator cars B, C and D. In some instances wherein a group of similar relays is employed only representative relays are shown in the control circuits and in the key representations.

Figure 1 The circuits of Fig. 1 include a manually operable switch 77 which is operated to its lower position as viewed in Fig. 1. (It should be noted that the switch 77 in Fig. 5 of the Santini et al. patent is illustrated therein as operated to its upper position.) In its lower position, the switch 77 connects the high-call reversal relay HCM through the make contacts QL1 of the load car quota relay across the buses L1 and L2. Closure of the make contacts QL1 indicates that a substantial demand for service in the up direction exists at the lower terminal floor. For example, the make contacts QL1 close when a predetermined number of elevator cars is fully loaded and travels up from the lower terminal floor within a predetermined time.

When the high-call reversal relay HCM is energized throughthe make contacts QL1, it establishes a holding circuit through its make contacts HCM2 and the normally-closed contacts of a cam-operated switch 79. The switch 79 is repeatedly opened at intervals determined by rotation of a cam 79C which is rotated at a substantially constant speed in any suitable manner, as by an induction motor 79M. Consequently, if the contacts QL1 are open at the same time that the switch 79 is opened by its cam, the holding circuit for the high-call reversal relay HCM is' interrupted and this relay resets.

Figure 2 As is mentioned in the Santini et al. patent, the elevator cars park at the lower terminal floor. Let it be assumed that all of the elevator cars are parked and that their motor-generator sets (not shown) are shut down. If the elevator car A is selected as the next elevator car to leave the lower terminal floor and if its starting relay SL (not shown) operates to initiate a starting of the elevator car A, the make contacts SL7 close to connect the coil of the motor-generator starting switch MG across the buses L1 and L2. In response to such energization of the motor-generator starting switch, the switch closes certain contacts for the purpose of starting the motorgenerator set of the elevator car A and for the purpose of connecting certain circuits for energization from the buses L1 and L2.

The motor-generator starting switch also closes its contacts MG6 to prepare a holding circuit which is completed either through the break contacts 78-4 of the no-call relay 78 (not shown) or through the make contacts MGTl-of the timing relay MGT. This holding circuit remains closed as long as a call remains registered in the system which may be answered by the elevator of the no-call relay 78 remain closed. The holding circuit also remains closed for a predetermined time after all of the elevator cars have parked at the lower terminal floor. During this period, the make contacts MGTl remain closed.

After all of the elevator cars have parked at the lowerterminal floor for a predetermined time with no further calls registered in the system, it may be desirable that all of the motor-generator sets be shut down. This control of the motor-generator sets is efiected by the timing relay MGT, which has a substantial delay in drop out. The delay in drop out of the relay MGT may be provided in any desired way. Such a delay is represented in Fig. 2 by a resistor RE10 which is connected across the coil of the relay. The relay MGT is energized through four make contacts M11, BM11, OM11 and DM11 of the running relays for the four elevator cars and through make contacts OHPl of the off-hours prevention relay OHP, and these contacts are connected in parallel for the purpose of controlling the energization of the timing relay.

Assuming a manually operable switch to be in closed condition, the off-hours prevention relay OHP is connected for energization through break contacts DP14 and make contacts HCM8 of the down-peak and highcall reversal relays DP (not shown) and HCM, respectively. Pick-up of the relay OHP is accompanied by closure of its make contacts OHP2 to establish a holding circuit for the relay through the break contacts DP14.

Let it be assumed that the elevator car A reaches the lower terminal floor, that the elevator cars B, C and D are parked at the lower terminal floor and that the relay OHP is in deenergized condition. When the elevator car A reaches the lower-terminal floor, the make contacts M11 of its running relay M (not shown) open. Since the make contacts BM11, CM11, and DM11 also are open, the timing relay MGT starts to time out. If the elevator car A starts before the relay MGT drops out, the contacts M11 reclose to reenergize the timing relay. However, if the elevator car fails to start within the drop-out time of the relay MGT, this relay drops out to open its make contacts MGTl and similar contacts associated with the elevator cars B, C and D. If no call is registered which may be answered by the elevator car A, the break contacts 78-4 of the no-call relay 78 also are open. Consequently, the holding circuit for the motor-generator starting switch MG is interrupted and this relay drops out to shut down the motor-generator set for the elevator car A.

As long as the make contacts OHPI are closed, however, the timing relay MGT cannot time out to open its make contacts MGTl, and the holding circuit for the motor-generator starting switch MG thus cannot be interrupted by the opening of the contacts 78-4. Consequently, the motor-generator set for the elevator car A (and for the cars B, C and D), if running, cannot be shut down as long as the elf-hours prevention relay OHP remains picked up.

Figure 3 In Figure 3, circuits are shown for controlling the dispatching interval quota relay QB and circuits are illustrated for the dispatcher for the upper terminal floor.

The intensity of traffic in the elevator system may be measured by measuring the number of stops made by the elevator cars. The measuring apparatus includes a notching or stepping switch SS, whose operation is fully described in the Santini et al. patent. Briefly, the stepping switch SS includes a pair of diametrically-opposite contact arms 201 and 203, which are mounted for rotation about an axis 205. The coil of the stepping switch is energized and deenergized once for each stop of each of the elevator cars which is to be counted. Since the 7 manually operable switches 150, B150, C150 and D150 are illustrated in Fig. 3 in closed condition, the energizing circuits for the coil of the stepping switch SS measure the number of stops made by the elevator cars for both directions of car travel. (In Fig. 7 of the Santini et al. patent, these switches are illustrated in open condition.)

For each stop of an elevator car, the contact arms 261 t and 203 advance successively to engage commutator segments' KS1 through KS9. Thus, the position of the contact arms indicates the number of stops made by the elevator cars. In addition, the time period relay K, which has a substantial time delay in drop-out, and the reset relay N cooperate to control the resetting of the stepping switch SS. Such resetting occurs each time the timeperiod relay K drops out after the expiration of its dropout time delay. I

The dispatching interval quota relay QB also has a time delay in drop-out, which is longer than the time delay in drop-out'of the time-period relay K. Such delay is determined, at least in part, by a resistor REll which is connected across the. relay. The relay QB is connected between the commutator segment KS4 and the bus L2 through break contact N5 of the reset relay N. The lower part of'Fig. 3 illustrates circuits for the upper terminal dispatcher. This dispatcher controls the selection of each elevator car to leave the upper terminal floor and initiates the starting of each elevator car from the floor.

The selection of the next elevator car to be dispatched from the upper terminal floor is effected by a selecting mechanism which includes a constant speed motor 8ST, an electromagnetic clutch RCT, a cam 871 and switches YT, BYT, CYT and DYT. These components operate in precisely the same manner as that described in the Santini et alpatent. sary to describe such operation further.

The dispatching system also starts each of the cars I from the dispatching floor after the expiration of a suitable dispatching interval. To this end, the motor SST is releasablycoupled by an electromagnetic clutch SCT to a timer cam 89T. When the winding SCT is energized, the cam 89T rotates away from a starting position successively to operate earn-operated switches 911 and 92T, which are biased toward their open conditions, by means of a cam projection 90T. When the electromagnetic clutchcoil-SCT is deenergized, a spring 93T returns the cam 891 to its starting position. The switch MT is so positioned that the time required for the projection 961" of the timer cam 89T to reach and close the switch 921" upon energization of the magnetic clutch SCT is substantially longer than the time required for the projection to reach and close the switch 911". Thus, the upper interval-holding relay ISD, which initiates the starting of a selected elevator car from the upper terminal floor is controlled in part by operation of the switches 91'1" and 92'1.

It will be observed that the upper-interval-holding relay lSD also is controlled by operation of an upper dispatching interval relay DT, with which are associated break contacts DT1 and make contacts DTZ. These contacts, in turn, are arranged'in series circuit connection with the cam operated switches 91T and 92T, rcspecti-vely. Energization of the dispatching interval relay DT is controlled through the serially connected make contacts QBl of the displatching interval quota relay QB, HCM6 of the high-call reversal relay HCM and DP15 of thedown-peak relay DP.

Figure 4 v Fig. 4 partially illustrates circuits for a lower'terrninal ponent in the two dispatchers are similar in construcl -i P 'at ou. Or this reason, each component of the lower dispatcher which issimilar to a component For this reason, it appears unneces- Insofar as the circuits involved in the illusof the upper dispatcher is identified by the same reference character except that the sufiix letter T for an upper dispatcher component is replaced by the suffix letter L for designating the corresponding lower dispatcher component. Thus, the upper dispatching interval relay. DT for the upper dispatcher corresponds to the lower dispatching interval relay DL for the lower dispatcher and operates in the same manner. For these reasons it is believed unnecessary to discuss in detail the components of the lower dispatcher which are similar to those of the upper dispatcher.

Operation From the drawings illustrating the invention and from the foregoing discussion, it is possible to trace theoperation of the system, as affected by the modifications of the invention, in response to various demands for elevator service. However, because of the complexity of the system it will be helpful at this stage to describe a number of representative operations of the system.

For the first operation to be discussed, it willbe assumed that all of the elevator cars are parked at the lower terminal floor with their motor-generator sets shut down. At this stage, the demand for elevator service increases to a point wherein the motor-generator sets of the elevator cars are successively placed in operation by a sequence which will be clear from the aforementioned mediately before the start of a business day.

Such operation results in the closure of the make contacts QL1 (Fig. l) of the loaded car quota relay QL to energize the high-call reversal relay HCM. Closure of the make contacts HCM8 (Fig. 2) results in pickup of the off-hours prevention relay OHP through the closed break contacts DP14 and the closed switch 100. Closure of the make contacts OHP1 has no immediate effect on system operation, since, under the assumed conditions, one or more of the parallel make contacts M11, BM11, CM11 and DM11 of the running relays associated, respectively, with the elevator cars A, B, C and D are in closed condition. Closure of the make contacts OHPZ establishes a holding circuit for the relay OHP through the closed break contacts DP14 and the closed switch 100.

Assume next that the trafiic demand decreases to a point such that the high-call reversal relay HCM drops out to open its make contacts HCM8. It will be observed that the relay OHP, however, remains picked up through its holding circuit. 7

if the decrease in traffic demand is such that all of the elevator cars subsequently'park at the lower terminal floor with no further calls registered in the system, all of the make contacts M11, BM11, CM11 and DMll will be in open condition. In the absence of the make contacts OHP1, a timing-out action of the timing relay MGT would occur, subsequently to shut down each of the motor-generator sets associated with each of the elevator cars by a sequence of operation'which will be apparent from the foregoing description of Fig. 2. The now .closed contacts OHP1, however, prevent the timing out of the relay MGT.

By inspection of Fig. 2, it will be observed that the olfhours prevention relay OHP cannot be deenergized until the break contacts DP14 open. Furthermore, such opening will not occur until the down-peak relay DP picks up in response to a peak demand for elevator service in the down direction, as is explained in the Santini et al. patent, It will be recalled that such down-peak generally occurs at the end of the'business day. Thus, during the business day, the motor-generator sets of all of the elevator cars are maintained in running condition regardless of the decrease in trafiic demand. As a result thereof, the elevator system is more quickly transferred to the required mode of operation upon the occurrence of heavy or peak periods of traffic after a period of little or no traflic demand, since the delay involved in the starting up of the motor-generator sets is eliminated.

For those installations wherein occasional up-peaks in trafiic may be encountered during the night after regular business hours, the manually-operable switch 100 may be opened to place make contacts 101 of a Timer in operative condition. When the switch 100 is opened, the make contacts 101 are placed in series with the off-hours prevention relay OHP, and the relay OHP cannot be energized unless the contacts 101 are in closed condition. The Timer may be designed to effect closure of its make contacts at 7:30 am. and opening thereof at :30 p.m., for example. Thus, when the switch 100 is in open condition, the off-hours prevention relay OHP is prevented from picking up in response to an up-peak in trafiic except immediately before or during regular business hours. It will be recalled that it is primarily during such hours that it is desired to prevent the elevator system from transferring to off-hours operation.

Let it next be assumed that the elevator system is conditioned for off-peak operation, that is, that the elevator cars provide balanced through-service in the two directions of travel between the lower and upper terminal floors. It will further be assumed that the contact arms 201 and 203 are in their reset positions as is shown in Fig. 3 and that the dispatching interval quota relay QB is Picked up but is timing out.

Since the relay QB is picked up, its break contacts QBl are in open condition and the upper dispatching interval relay DT is, therefore, dropped out. When the electromagnetic clutch coil SCT is energized, the timer cam 89T rotates away from its starting position to opcrate the cam-operated switch 91T to complete the following circuit: Ll, 1SD, 91T, DT1, HCMS, ST4, BST4, CST4, DST4, L2. (It is assumed that the contacts ST4, BST4, CST4 and DST4 all are closed, i.e., no car previously has been assigned to start from the dispatching floor.) Thus, as long as the relay DT remains deenergized the dispatching interval between successive selected elevator cars is controlled by operation of the switch 91T. The cam-operated switch 91L (Fig. 4) associated with the lower terminal floor dispatcher operates in a similar manner to determine the dispatching interval between successive selected elevator cars from the lower terminal floor.

During the time required for the relay QB to drop out, the contact arms 201 and 203 are advanced one step for each counter car stop made by the elevator cars in service in the elevator system. It will be assumed first that two stops are made by the elevator cars before the dispatching interval quota relay QB drops out. Consequently, the contact arm 201 is in engagement with the commutator segment KS3 at the time the relay QB drops out.

Dropout of the relay QB is accompanied by closure of its break contacts QBI to pick up the upper dispatching interval relay DT through the following energizing circuit: L1, DT, QBl, HCM6, DP15, L2. Pickup of the relay DT results in the opening of its break contacts DT1 and the closure of its make contacts DT2.

In this instance, when the winding of the electromagnetic clutch SCT is energized, the cam 89T will rotate away from its starting position first to operate the switch 91T and subsequently to operate the switch 92T. Since the break contacts DT1 now are open, closure of the switch 91T by operation of the cam has no effect on the operation of the system. Closure of the switch 92T by operation of cam 89T, however, results in the completion of the following energizing circuit for the upperinterval-holding relay 1SD: L1, 1SD, 92T, DTZ, HCMS, ST4, BST4, CST4, DST4, L2. Thus, pick-up of the upper dispatching interval relay DT results in an increase in the dispatching interval between successive selected elevator cars, such increase being the difference between the time required for the projection 901 of the cam 89T to reach the switch 92T from its starting position and that required for the projection to reach the switch 91T from its starting position. Similarly, the cam-operated switch 92L (Fig. 4) operates to increase the lower terminal dispatching interval.

Next it will be assumed that while the contact arm 201 is in engagement with the commutator segment KS3 and the relay QB is dropped out, the time-period relay K times out to initiate a resetting operation of the stepping switch SS. Such resetting operation will be clear from the aforementioned Santini et al. patent. As is ex- 1 plained therein, during the resetting operation of the switch SS, the reset relay N is picked up. The resulting opening of the break contacts N5 prevents reenergization therethrough of the dispatching interval quota relay QB during the resetting operation.

It now will be assumed that the elevator cars make a total of three counted stops before the dispatching interval quota relay QB and the time-period relay K time out. When the contact arm 203 reaches the commutator segment KS4, an energizing circuit is established for the relay QB as follows: L1, 201, KS4, QB, N5, L2. The relay QB, therefore, remains picked up to maintain its break contacts QBl and QB2 in open condition, and the upper and lower dispatching interval relays DT and DL, respectively, remain dropped out. Thus, a normal dispatching interval is maintained between successive selected elevator cars from the upper and lower terminal floors, as will be clear from the foregoing description of operation.

It will be observed that as long as the rate of elevator cars stops, as counted by the stepping switch SS, is sufiicient to prevent the relay QB from timing out, successive selected elevator cars are dispatched from the upper and lower terminal floors at normal dispatching intervals. However, if the rate of car stops decreases to a point such that the relay QB times out to Pick up the dispatching interval relays DT and DL, indicating relatively light traffic, the dispatching interval between successive selected elevator cars is increased.

The dispatching interval quota relay QB is provided with a time delay in dropout which is longer than the time delay in dropout of the time period relay K in order that the stepping switch SS may reset and count stops of the elevator cars before the relay QB drops out. Such operation prevents hunting of the system between normal and increased dispatching intervals due to a resetting operation of the stepping switch SS.

It is desired that the normal dispatching intervals at the upper and lower terminal floors be maintained between successive selected elevator cars during up-peak and down-peak operation of the elevator system regardless of the rate of elevator car stops during either of such operations. Since the high-call reversal relay HCM and the down-peak relay DP are picked up during uppeak and down-peak periods of system operation, respectively, the break contacts HCM6 and DP15 (Fig. 3) prevent pickup of the upper dispatching interval relay DT to increase the upper terminal dispatching interval during up-peak and down-peak operation. Similar con tacts, HCM7 and DP16 (Fig. 4), are provided to effect similar results in the circuit of the lower dispatching interval relay DL.

Although the invention has been described with reference to certain specific embodiments thereof, numerous modifications falling within the spirit and'the scope of the invention are possible.

'- of landings, an elevator car, means mounting the elevator car for'movement' relative to the structure to serve the landings, motive means for moving the elevator car rela- I tive to'the structure, a source of energy for the motive means, said source having an operating and a non-oper- 7 ating Condition, and'control means for controlling the starting and the stopping of the elevator car, said control means comprising registering means for registering demand for elevator service, first control means for placing said source of energy in operating condition in response to the registration by said registering means of a first predetermined demand for service and for placing the operating source of energy in non-operating condition in response to decrease of the demand for service below a predetermined value, and second control means responsive to' a'second predetermined demand for service for preventing said operating source of energy from being placed in non-operating condition by said first control means despite subsequent decrease in the demand for service below said predetermined value except upon the occurrence of a third predetermined demand for service.

I 2; In an elevator system, a structure having a plurality of landings, a plurality of elevator cars, means mounting the elevator carsfor movement in two directions relative :to the structure to serve the landings, separate motive means for moving'each of the elevator cars relative -to thestructure, a separate source of energy for each of the motive means, each of'the sources having an operating and a non-operating condition, and control means for controlling the starting and the stopping of the elevator cars, said control means comprising first registering means for registering demand for elevator service in a first-of said two directions, second registering means for registering demand for elevator service in the second of said two directions, first control means for placing the source of energy of each of the elevator cars in operating condition in response to the registration by said 'first and second registering means of a first predetermined demand for service and for placing each operating source of energy in non-operating condition in response to decrease of the demand for service below a predetermined value, second control means responsive to a second predetermined demand for service for prevent-.

ing each operating source of energy from being placed in non-operating condition by said first control means despite subsequent decrease in the demand for service be low'said predetermined value, and third control means responsive to a third predetermined demand for service, for rendering said second control meansineffective to prevent each operating source of energy from being placed in nonoperating condition by said first control means. 3. In an elevator system, a structure having-aterminal landing and a plurality of'landings spaced in a first direc-., -tion from said terminal landing, a plurality of elevator cars, means mounting the elevator cars for movement relative to the structure in-saidfirst direction and in a elevator service, said registering means including call registering means operable from each of said plurality "of landings for registering calls forelevator service in said second direction from the associated landing,'dispatching means for selecting one elevator car at a time present at the terminal landing as the next elevator car to be dispatched and for initiating startingofthe selected ielevator'car to answer a predetermined-demand"for elevator service registered by-tt-the .registering-meansgfirst i said terminallanding upon lapse of a time which is control means'for placing the source of energy of each of the selected elevator cars in operating condition in response to the registration by said registering means of 1 a predetermined demand for service and for placing each operating-source of energy in non-operating condition in response to, decrease of the demand for service below a predetermined value-second control means responsive to a second predetermined demand for elevator service in said first direction from said terminal landing for preventing each operating source of energy from being placed in non-operating condition by said first control means despite subsequent decrease in the demand for service below said predetermined value, and third control means responsive to the registration by said call registering means of at least a, predetermined number of calls for elevator service in said second direction for rendering said second controlmeans ineffective to prevent each operating source of energy from being placed in non-operating condition by said first control means.

4. In an elevator system, a structure having a plurality of landings including a terminal landing, a plurality of elevator cars, meansmounting the elevator cars for movement relative to the structure to serve the landings,

- separate-motive means for moving each of the elevator cars relative to the structure stopping means for each of the elevator cars, and controlmeans for controlling the movement of the elevator cars by the motive means and the stopping'of the elevator cars at predetermined landings, said control means comprising selective means operable into at least a first condition to control the elevator cars for a first mode of operation, dispatching means for selecting one'elevatorcar-at a time present at the terminal landing asthe next elevator car to be dispatched from the terminal landing and for initiating starting of the selected elevator car from the terminal landing, timing means responsive to at least a predetermined rate of stops at said landings of all of the' elevator cars for requiring lapse of a predetermined minimum time between the startings of successive selected elevator cars from the terminal landing when the elevator cars are conditioned for said first mode of operation, and means responsive to less than saidpredetermined rate of stops when the elevator cars are conditioned for said first mode of operation for adjusting the timing means to permit the startings of successive selected elevator cars from 7 greater than-said predetermined minimum time.

5. In an elevator system for a structure having a plurality of landings including a first terminal landing, a second terminal landing and a plurality of intermediate landings located between the terminal landings, a plurality of elevator cars, means mounting the elevator cars for movement relative to the structure in each of two direc tions to provide elevatorservice for the landings, sep arate motive means for moving each of the elevator cars relative to the structure, stopping means for each of I the elevator cars, and controlmeans for controlling the movement of the elevator cars by the motive means and the stopping of the elevator cars at predetermined landings, said control means comprising selective means operable into at least a first condition to control the ele* vator carsfor a first mode of operation, dispatching means for successively selecting'elev'ator cars to be dispatched -from each of the terminal landings and for initiating starting of each selected elevator car from the associated terminal landing, timing means responsiveto at least a predetermined rate of stops at all ofsaid landings of all of theelevator cars for requiring lapse of a predetermined minimum time between the startings of successive selected elevator cars from the associated terminal landing when the elevator cars are conditioned for said first mode of operation, and'means responsive to less than said predetermined rate of 'stops'when the elevator cars are con- ---ditio'ned for said first mode'of operation for-adjusting'the timing means to permit the-startings of successive selected elevator cars from the associated terminal landing upon lapse of a time which is greater than said predetermined minimum time, said elevator cars in said first mode of operation providing an oil-peak operation which is sub stantially balanced in the two directions of travel.

6. In an elevator system, a structure having a plurality of landings including a terminal landing, a plurality of elevator cars, means mounting the elevator cars for movement relative to the structure to serve the landings, separate motive means for moving each of the elevator cars relative to the structure, a separate source of energy for each of the motive means, each of the sources having an operating and a non-operating condition, stopping means for each of the elevator cars, and control means for controlling the movement of the elevator cars by the motive means and the stopping of the elevator cars at predetermined landings, said control means comprising registering means for registering demand for elevator service, first control means for placing the source of energy of each of the elevator cars in operating condition in response to the registration by said registering means of a first predetermined demand for service and for placing each operating source of energy in non-operating condition in response to decrease of the demand for service below a predetermined value, second control means responsive to a second predetermined demand for service for preventing each operating source of energy from be- '14 ing placed in non-operating condition by said first control means despite subsequent decrease in the demand for service below said predetermined value except upon the occurrence of a third predetermined demand for service, selective means operable into at least a first condition to control the elevator cars for a first mode of operation when said second control means is operative to prevent each operating source of energy from being placed in non-operating condition by said first control means, dispatching means for selecting one elevator car at a time present at the terminal landing as the next elevator car to be dispatched from the terminal landing and for initiating starting of the selected elevator car from the terminal landing, timing means responsive to a first predetermined traflic condition for requiring lapse of a predetermined minimum time between the startings of successive selected elevator cars from the terminal land-- ing when the elevator cars are conditioned for said first mode of operation, and means responsive to a second predetermined trafiic condition when the elevator cars are conditioned for said first mode of operation for adjusting the timing means to permit the startings of successive selected elevator cars from said terminal landing upon lapse of a time which is greater than said predetermined minimum time.

No references cited. 

